Shape-transferring cannula system and method of use

ABSTRACT

A medical cannula system comprises a conduit; an endoscope comprising a distal steerable tip, wherein the endoscope is inside the conduit, and wherein the distal steerable tip of the endoscope extends out of the conduit; a tip liner surrounding the distal steerable tip of the endoscope; and a wiper link surrounding the tip liner at a close tolerance.

RELATED U.S. PATENT APPLICATION

This application is a continuation of U.S. application Ser. No.13/087,156, filed Apr. 14, 2011, which is a continuation of U.S.application Ser. No. 11/479,704, filed Jun. 30, 2006 (now U.S. Pat. No.7,947,000), which is a continuation-in-part of U.S. application Ser. No.10/661,159, filed Sep. 12, 2003 (now U.S. Pat. No. 8,298,161), whichclaims priority to U.S. Provisional Application No. 60/409,927, each ofwhich is incorporated by reference in its entirety. This applicationalso is related to U.S. application Ser. No. 10/899,561, “Cannula Systemand Method of Use”, by an inventor of this patent application, filedJul. 27, 2004, the entirely of which is incorporated herein byreference.

FIELD OF THE INVENTION

The present invention relates to devices, systems, and processes usefulfor exploration of hollow body structures, particularly those areasaccessed through a tortuous, unsupported path. More particularly, thepresent invention relates to a shape-transferring cannula device thatcreates a custom-contoured access port for insertion and removal ofdiagnostic, surgical, or interventional instruments to and from a sitewithin the body to which the physician does not have line-of-sightaccess.

BACKGROUND OF THE INVENTION

Surgical cannulas are well known in the art. Such devices generallyinclude tube-like members that are inserted into openings made in thebody so as to line the openings and maintain them against closure.Surgical cannulae can be used for a wide variety of purposes, and theirparticular construction tends to vary accordingly (see, e.g., U.S. Pat.No. 5,911,714). Flexible endoscopes, endovascular catheters andguidewires, and trocar cannulae such as those used in laparascopicsurgery, are examples of such devices. Several U.S. patents recite suchdevices. See, for example, U.S. Pat. Nos. 5,482,029; 5,681,260;5,766,163; 5,820,623; 5,921,915; 5,976,074; 5,976,146; 6,007,519;6,071,234; and 6,206,872.

All of these devices are in use in one form or another and they arehelpful to some extent, but they also pose several problems. Flexibleendoscopes and endovascular catheters rely on reaction forces generatedby pushing against the tissue of the body cavity being explored tonavigate around corners or bends in the anatomy. This approach worksreasonably well for small-diameter endovascular catheters that aretypically run through arteries well supported by surrounding tissue. Inthis case the tissue is effectively stiffer than the catheter orguidewire and is able to deflect the catheter's path upon advancementinto the vessel. The approach is much less successful in the case offlexible endoscopes being guided through a patient's colon or stomach.In these cases the endoscope is either significantly stiffer than thebody cavity tissue it is being guided through or, as is the case for thestomach or an insufflated abdomen, the body cavity is sufficientlyspacious that the endoscope has no walls at all to guide it. In the caseof colonoscopy, the endoscope forces the anatomy to take painful,unnatural shapes. Often, the endoscope buckles and forms “loops” whenthe colonoscopist attempts to traverse tight corners. Pushing on the endof the flexible endoscope tends to grow the loop rather than advance theendoscope. “Pushing through the loop” relies on the colon to absorbpotentially damaging shapes of force to advance the endoscope. In casesof unusually tortuous anatomy, the endoscope may not reach its intendedtarget at all, leaving the patient at risk of undiagnosed andpotentially cancerous polyps.

Endovascular catheters have drawbacks as well. While generally flexibleenough to avoid seriously damaging the vessel's endothelial surface,guidewires are difficult to guide into small side branches of largevessels such as the coronary ostia or into relatively small vesselsconnecting to relatively large chambers such as the pulmonary veins.Catheters are even more limited in their ability to deal with greatlytortuous vessel anatomy such as the vessels radiating from the brain'sso-called Circle of Willis.

U.S. Pat. No. 5,251,611 (Zehel) discloses the use of one or morerigidizable conduits for conducting exploratory procedures. A particularrigidizable conduit disclosed by Zehel includes a series of nestedsegments that are traversed by a plurality of cables or wires. Tensionis applied to the wires to press the segments together, therebyproducing a stiffened conduit. A side effect of the compression reactionto the applied tension is a shortening of the conduit as the segmentsare pressed together. For procedures involving an instrument that isinserted in the conduit, he shortening of the conduit will result in achange in the relative position of the instrument and the conduit. Thischange in relative position may have an adverse effect on the placementor use of the instrument.

Ablation and EKG mapping catheters used in cardiologicalelectrophysiology find their intended targets chiefly by trial and errorinsertion and twisting of a guidewire/catheter accompanied by grossmotions of the entire catheter. A need, therefore exists for a cannulasystem that provides access port for insertion and removal ofdiagnostic, surgical, or interventional instruments to and from a sitewithin the body to which the physician does not have line-of-sightaccess. Furthermore, there is a need for cannula systems that can followa tortuous path through hollow soft-tissue structures without relying onthe surrounding tissue to mechanically support and guide its insertionand may be steered and advanced directly to an anatomical point ofinterest. There is also a need for a cannula system that can accommodateshortening in the cannula and maintain a relative position between thecannula and an instrument inserted therein as well as between thecannula and a target site within the body.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic sectional view of the shape transferringcannula system illustrating the major components.

FIGS. 2A-2D illustrate diagrammatic sectional representations of asequence of rigidizing structure stiffening, relaxing, and advancementthat enables guiding of the shape transferring cannula.

FIG. 3 is a perspective view of an embodiment of laterally parallelrigidizing core and sheath linkage structures.

FIGS. 4A and 4B illustrate perspective views of captured-link rigidizinglinkages.

FIG. 5 is a perspective view of a cable-rigidized core linkage.

FIG. 6 shows perspective and sectional views of a cable-rigidized sheathlinkage.

FIG. 7 is a sectional view of an off-axis tensioning mechanism for acable-rigidized sheath linkage.

FIG. 8 is a perspective view of an alternate embodiment of a laterallyparallel sheath linkage.

FIG. 9 is a sectional view of a laterally parallel sheath linkage.

FIG. 10. shows perspective and end views of an open-sided sheathlinkage.

FIG. 11 is a perspective view of a laterally parallel sheath linkagewith compliant elements.

FIGS. 12A-12H illustrate various views of an alternating advancementmechanism in accordance with the present invention.

FIGS. 13A-13C is a perspective view of a rotating link cannula structure

FIGS. 14A-14C is a diagrammatic view of a cannula structure including apassive element.

FIG. 15 is a sectional view of a continuous stiffening cannulastructure.

FIG. 16 is a perspective view of a cannula structure formed withnormally-rigid, thermally relaxing materials.

FIGS. 17A and 17B illustrate sectional views of vacuum-stiffeningcannula structure elements.

FIG. 18 is a sectional view of a pressure-stiffening cannula structure.

FIGS. 19A and 19B show a sectional view of normally-rigid, vibrationallyrelaxing cannula structure elements.

FIGS. 20A and 20B illustrate sectional views of a cannula structureincluding active material elements.

FIG. 21 is a perspective view of two-axis pivoting links.

FIG. 22 depicts a catheter with a shape-transferring section.

FIG. 23 depicts a thermally relaxing normally-rigid structure.

FIG. 24 depicts a motorized advancement mechanism.

FIG. 25 depicts a rigidizable cannula with distal recirculation.

FIG. 26 depicts a rigidizable cannula with proximal recirculation.

FIG. 27 depicts a rigidizable cannula with dual recirculation.

FIG. 28 depicts a rigidizable cannula wiper tip with distalrecirculation.

FIG. 29 depicts a for dual cannula system with an endoscope liner andexternal cover.

FIG. 30A depicts an endoscope with handle and actuators for dual cannulasystem in an extended configuration.

FIG. 30B depicts an endoscope with handle and actuators for dual cannulasystem in a retracted configuration.

FIG. 31A depicts a cannula system with an endoscope and reference framehandle in a relaxed configuration.

FIG. 31B depicts a cannula system with an endoscope and reference framehandle in a rigidized configuration.

FIG. 32 depicts a flow diagram of a method embodiment in accordance withthe present invention.

FIG. 33A depicts an endoscope with a cannula system including a distalinflatable balloon.

FIG. 33B depicts an endoscope with an inflatable balloon and a cannulasystem with a distal inflatable balloon.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a novel shape-transferring cannulasystem, which provides access to tortuous and unsupported paths. Theshape-transferring cannula system and method enables exploration ofhollow body structures, and creates a custom-contoured access port forinsertion and removal of, for example, diagnostic, surgical, orinterventional instruments to and from a site within the body to whichthe physician does not have line-of-sight access.

The shape-transferring cannula can follow a tortuous path through hollowsoft-tissue structures without relying on the surrounding tissue tomechanically support and guide its insertion. The system includes twoparallel rigidizing sections that alternatingly stiffen and relax withrespect to one another and alternatingly transfer the path shapetraced-out by the articulating tip to one another. A steerablearticulated tip is attached to one of the rigidizing sections. Thecannulas custom shape is formed by guiding the articulated tip along adesired path direction, stiffening the attached rigidizing section, andadvancing the other rigidizing section along the stiffened section.

The end of the shape-transferring cannula may be steered and advanceddirectly to an anatomical point of interest. The user traces a path forthe shape-transferring cannula with the steerable tip and in doing sodefines the longitudinal shape assumed by the cannula, thus directingthe working end of the cannula to a target site without substantiallydisturbing the length of cannula behind it. The ability to navigatepredictably within heart chambers and swap out catheters from arelatively fixed position, for example, greatly improveselectrophysiologists' ability to methodically locate and ablate theectopic foci responsible for atrial fibrillation and other cardiacarrhythmias.

The ability to localize movements to the user-controlled tip of thecannula is especially valuable when working within particularlysensitive open structures such as the ventricles of the brain or looselysupported, tortuous structures such as the colon that provide verylittle mechanical support for intubation around corners.

The shape-transferring cannula system assumes the shape traced by thepath of the articulating tip in an incremental fashion, with the coreand sheath rigidizing structures transferring the traced path shape backand forth to each other. Having reached the target site, the externalsheath can be made flexible and slid out over the rigidized centralcore. Unlike the lengthy re-intubation procedure for a conventionalflexible endoscope, returning to the target site is simply a matter ofsliding the sheath or surgical instruments over the core that now actsas a guidewire. Alternately, the sheath may be left rigid and in placeonce having reached the target site and the core may be made flexibleand removed. This leaves the shaped sheath to act as a cannula throughwhich surgical instruments such as snares, ultrasound probes, biopsyprobes and other diagnostic devices, electrocautery tools, and the likemay be transferred to and from the target site.

The individual elements of the invention have useful applicationsindependent of the full system. For instance, the rigidizing sheathstructure may be used on its own as a rigidizing cannula when introducedto a target site by a conventional guidewire, flexible endoscope, orsimilar introduction element. Unlike conventional rigid cannulae, therigidizing cannula does not have a predetermined longitudinal shape.Yet, when stiffened, the rigidizing cannula may support reaction forceslike a rigid cannula when tools are run down its length, thus protectingsensitive tissue structures.

The present invention will now be described in detail with reference tothe following drawings. FIG. 1 depicts a preferred embodiment of ashape-transferring cannula system 1 d having two parallel rigidizingcore 1 and sheath 2 structures, a steerable articulated tip 3 attachedto one of the rigidizing structures, a proximal end 1 a, a distal end 1b and a lumen 1 c through which surgical tools may be introduced orthrough which the target site may be irrigated or suctioned. The core 1and sheath 2 are parallel structures that can be coaxial or side-by-sideand that may be made rigid or flexible with respect to one another. Thecore and sheath structures may be unitary materials or continuousstructures, or they can be formed of individual, flexibly connectedrigid links. The core and sheath structure employs rigidizing cableswhich, when put into tension, pull the links together to increasefriction between links and prevent relative motion between the links.The core's rigidizing structure is built-up of links such that a convexspherical surface on one link engages a concave surface on an adjacentlink. The core's rigidizing cable runs through each core link's centralorifice, connecting the entire core rigidizing structure. The corelink's central orifice has a diameter D1 that is in the range from about0.5 mm to about 30 mm. Those of skill in the art will readily appreciatethat the particular application, e.g., device, to which the presentinvention is applied may require a particular diameter D1, and it iswithin the scope of the present invention to select an appropriatediameter D1 for the specific application. For example, a typicalendoscope employing structures in accordance with the present inventionmay have an inner diameter from about ¼ inch to about ½ inch, althoughlarger or smaller sizes may also be suitable.

The system employs a method of incremental advancement to deliver thedistal end 1 b of the cannula to a target site. The core 1 and sheath 2rigidizing structures are alternatingly advanced, one structure past theother, the stationary structure being made rigid and acting as a guidefor the advancing flexible structure. The steerable tip assembly 3 islocated on the end of at least one of the two rigidizing structures suchas the core 1 as depicted in FIG. 1. The steerable tip 3 may be actuatedvia cables or other tension members, magnetostrictive materials,bimetallic strips or other flexing elements, piezoelectric polymer filmsor ceramics, shape memory materials such as nickel-titanium shape memoryalloys or shape memory polymers, electroactive artificial musclepolymers, or the like. The length of the steerable tip 3 and the lengthL, described elsewhere herein, are preferably mutually selected to beabout the same length, so that the cannula can follow and track thesteerable tip (see FIG. 12G).

The overall length of the cannula will vary according to the particularhollow body structure for which it is intended. For instance, used in acolonoscope application the shape-transfer cannula length might rangefrom 100 cm to 180 cm. In a bronchoscope application the shape-transfercannula length might range from about 30 cm to about 100 cm. In acatheter application, the rigidizing core 1 and sheath 2 components of ashape-transfer cannula might be limited to a relatively small section ofthe entire catheter length, as depicted in FIG. 22. For example, thecore 1 and sheath 2 can be provided only at the distalmost end of thedevice or apparatus that is intended to be steered. In such a case themajority of the cannula's length include “passive” conventional extrudedcatheter material 251 and a non-rigidizing section of core 252. Forexample, in accessing particular areas within the heart's ventricles,the extra control provided by the shape-transferring core 1 and sheath 2components might only be needed within the ventricles themselves so thelength of the rigidizing section R, need only be sufficient to navigatewithin the ventricles themselves.

Another aspect of the present invention is that the distal, steerableportion of the apparatus has a shape-transforming length L and an outerdiameter D, with the ratio UD being at least about 5 (L/D>5), so thatthere is enough longitudinal length of the shape-transforming portion ofthe device or apparatus to track the steerable tip 3.

FIG. 2 illustrates by way of example a sequence in which the core 1 andsheath 2 alternate sequentially between rigid and flexible such that theentire structure takes the shape traced by the steerable tip 3 as theshape-transferring cannula is inserted into a hollow body structure suchas the colon, stomach, lung bronchi, uterus, abdominal cavity, brainventricle, heart chamber, blood vessel, or the like. In FIG. 2a , thesheath 2 is rigid and the core 1 with steerable tip 3 is flexible. Thesteerable tip 3 initially lies within and is approximately flush withthe distal end 1 b of the sheath 2 such that both the sheath 2 and core1 assume the same longitudinal shape whether curved or straight. Tobegin the sequence that advances and forms the longitudinal shape of theshaped cannula structure 1 d, in FIG. 2b the core 1 is advanced distallythrough the rigidized sheath 2, exposing the length of the steerable tip3. The user then directs the exposed steerable tip 3 in the desireddirection of insertion and advances the structure with, for example, asqueeze advancement mechanism (which will be discussed later herein) orthrough a cam mechanism or through any other structure or mechanism thatrigidizes and relaxes the core 1 and sheath 2 in proper sequence.Referring to FIG. 2c , to advance the entire shape-transferring cannulastructure 1 d, the core 1 is made rigid and then the sheath 2 is relaxedand, as shown in FIG. 2d , the sheath is advanced over the core 1 andsteerable tip 3. Preferably, the longitudinal relative motion betweenthe two rigidizing elements (i.e. core 1 and sheath 2) is limited to thelength of the steerable tip 3, the user-controlled element that servesas the system's directional guide. The sheath 2 is then made rigid andthe core 1 is relaxed and advanced to re-expose the steerable tip 3.Thus, in sequential fashion, the rigidizing structure portion of theshape-transferring cannula 1 d takes the shape of the path traced by thesteerable tip 3 as guided by the user.

Other sequences and combinations of stiffening, flexibility, andadvancement to achieve the same result are possible within the scope ofthis invention. For instance, the sheath 2 and core 1 may benormally-stiff structures that momentarily become flexible atappropriate times in the shape-transferring cannula advancementsequence. In another example, the sheath 2 and core 1 may benormally-flexible structures that momentarily become rigid atappropriate times to complete the advancement sequence. In anotherexample, the core 1 and sheath 2 may both include a steerable tip 3providing each structure with both directional control and the momentaryrigidity necessary for shape-transference

FIG. 3 depicts an alternative embodiment of a shape-transferring cannulasystem in accordance with the present invention. In this embodiment, theshape-transferring core 1 and sheath 2 are not necessarily coaxialstructures and may be laterally parallel structures that slidably engageeach other longitudinally via engagement features 10. In general,engagement features in accordance with the present invention includestructures that permit the core 1 and sheath 2 to slide or otherwisemove longitudinally relative to each other. One aspect of engagementfeatures in accordance with the present invention that one of the core 1and sheath 2 provides a rail for advancement of the other of the coreand sheath relative thereto.

At least one of the shape-transferring structures includes a steerabletip 3 with which to guide advancement of the system. Either or both ofthe shape-transferring structures can contain accessory lumens 11through which surgical tools may be introduced or through which thetarget site may be irrigated or suctioned. The engagement feature 10 ofeither structure can be used as a guide for withdrawing samples orinserting tools that won't fit through the accessory lumen 11. Outsizedtools may be provided with compatible engagement features such that theytrack along the guide formed by the rigidizing structure's engagementfeatures.

In a preferred embodiment of the present invention, the user's selectionof an advancement direction and his actuation of the system, whethermanual or powered, causes the entire cycle of core rigidization, sheathrelaxation, sheath advancement, sheath rigidization, and core relaxationto occur such that the structure is returned to its initial state with anew longitudinal shape.

The core and sheath structures may be unitary materials or continuousstructures that can be transformed between relatively rigid andrelatively flexible or they can be formed of individual, flexiblyconnected rigid links which become substantially locked together torigidize the structure. In an embodiment comprised of links, the sheathand core linkage structures are rigidized by temporarily preventing, byany suitable mechanism, substantial relative motion between the links.For example, motion between links may be temporarily stopped orsubstantially reduced by tightening a tension cable to put the linkageinto longitudinal compression, by electrostatic or magnetic forces, byhydraulic or pneumatic actuation, by changes in viscous coupling as withelectrorheological or magnetorheological materials, or through anyfriction modulating means.

Linkages may be held together by a flexible internal cable or externalcovering, or by attaching the links to each other while leaving enoughfreedom of rotation to make the structure longitudinally flexible. Morespecifically as shown in FIGS. 4A and 4B, the links may be looselycaptured by overlapping ball and cup features in adjacent links suchthat the cup features 22 overlap past the equators of the adjacent ballfeatures 23. This arrangement allows two-axis pivoting between linkswhile keeping the linkage intact. FIG. 4A illustrates a specific exampleof a rigidizing mechanism where sheath and core rigidizing linkagestructures may include a compression element 20 in each link, such as aloop of nickel-titanium alloy wire or shape memory polymer whoseshape-memory transition temperature is higher than normal bodytemperatures. A slot 24 in the cup 22 may facilitate compression of thecup against the ball 23 when the compression element 20 is actuated. Thecompression elements 20 in the links may be actuated through electricalor inductive heating or through any suitable means to activate theshape-memory effect such that the compression elements reduce theirunstressed diameters, creating local compression between ball and cup,and thus increasing friction between links.

FIG. 4B illustrates another example of a rigidizing mechanism employingthe same type of captured-link linkage configuration as the previousexample. In this embodiment, either the ball 23 or the cup 22 caninclude active material components 25 made of materials such aselectroactive polymer (EAP) that change shape when energized. The activematerial components may be oriented to expand radially when energized,causing interference between the ball and cup of adjacent links.Alternately, in a normally-rigid structure, the active materialcomponents 25 may be oriented to contract radially when energized,relieving interference between the ball and cup features of adjacentlinks.

By way of another example, linkages built of links made of dielectricmaterials may be rigidized electrostatically by building attractive orrepulsive charges between links and increasing friction between links.By way of another example, inducing magnetic attraction or repulsionbetween links containing ferromagnetic materials can stiffen arigidizing linkage by increasing friction between the links. By way ofanother example, linkages built with links made of conductive materialsmay be rigidized by inducing eddy currents that attract links to eachother and increase friction between links.

FIGS. 5 and 6 illustrate a linkage embodiment of parallel rigidizingsheath and core structure that employs rigidizing wires or cables 34 and40, which go through the core 1 and sheath 2 respectively. These cables,when put into tension, pull the links together to increase frictionbetween the links and thus prevent relative motion between the links.When not in tension, the rigidizing cables serve to hold the individuallinks in the rigidizing assembly together.

As illustrated in FIG. 5, the cores rigidizing structure 30 is built-upof links such that a convex spherical surface 31 on one link engages aconcave surface 32 on the adjacent link. FIG. 5 shows cup-like nestinglinks 33 with a spherical ball-joint-like interface that allows two-axispivoting between abutting links, thus making the linkage longitudinallyflexible. The core's rigidizing cable 34 runs through each core link'scentral orifice 35, connecting the entire core rigidizing structure 30.The steerable tip 3 control cables 36 may also run through each link'scentral orifice 35. The control cables 36 may be mechanical cablestransmitting tension or compression, or electrical connectionstransmitting power or signal to actuate or control the steerable tip 3.Alternatively, the rigidizing cable 34 and tip-steering cable 36 may becontained within individual lumens of a multilumen housing or withinindividual housings, keeping them separated and keeping the tip-steeringcables 36 from binding when the rigidizing cable 34 is tensioned tostiffen the core structure. The housing material may be chosen for lowfriction cable movement. One lumen of the multilumen housing might alsoserve to guide the core 1 along a conventional guidewire for rapidinsertion into guidewire accessible anatomy such as the atria andventricles of the heart.

Other linkage geometries that allow two-axis pivoting are possiblewithin the scope of this invention. For example as in FIG. 21, links 240with male 241 and female 242 pivot features that each rotate on only oneaxis can be alternated and mounted within each other, within therigidizing structure, with adjacent pivot features having axesperpendicular to one another. Thus, each pair of links 240 provides twoorthogonal pivoting axes to the linkage structure.

FIG. 6 illustrates a linkage embodiment of the sheath 2 in which thesheath links include a hollow central orifice 41 and pivot on sphericalball-joint like ball 46 and cup 47 surfaces for two-axis pivoting. Thesheath's rigidizing cable 40 runs outside each sheath 2 link's centralorifice 41 allowing the assembled links to form a hollow central lumen42 that can be occupied by the core 1 structure during cannulaadvancement as well as by items such as surgical instruments which thesheath lumen 42 can guide to a surgical or diagnostic site. The link'scentral orifice 41 has a diameter D2 that is substantially similar todiameter D1, described above.

The rigidizing sheath links 45 may include at least two cable-guidingfeatures 44 external to the central lumen 42. The cable 40 andcable-guiding features 44 are configured for low friction sliding.Friction may be further reduced by encasing the cable in a cable housingformed of a material with low-friction properties, such as PTFE, HDPE,and the like, thus separating it from the cable-guiding features 44.Alternatively, the cable-guiding features themselves could bemanufactured from low friction materials different from that of the restof the links. When the links 45 are assembled into a rigidizingstructure 46, the cable-guiding features 44 form segmented channelsrunning the length of the rigidizing structure 46. Since the cables 40do not run down the central axis of the sheath 2, cables running onopposite sides of the sheath 2 must effectively change length when thesheath 2 bends, Cable segments closer to the center of curvaturerelative to the structure's neutral axis will have to shorten. Likewise,cable segments further from the center of curvature relative to thesheath's 2 neutral axis will have to lengthen.

An embodiment of a linkage sheath with two cable-guiding channels anequal radial distance from the sheath's central axis may employ thesingle cable 40 wrapping around a pulley 43, which may be a rotatingcomponent, sliding surface, or the like, to run back and forth along thelength of both cable-guiding channels. As the structure bends, the innercable path will shorten the same amount as the outer cable pathlengthens and cable length will move from the shortening side around thepulley 43 to the lengthening side. Tension on the pulley 43 with respectto the linkage structure 46 tightens the entire cable 40 and stiffensthe sheath 2 by increasing friction between the links. Referring to FIG.7, the sheath's tensioning pulley 43 may be positioned off-axis suchthat the sheath central lumen 42 is clear and able to receive the core 1or surgical instruments. A cable-guiding element 50 at the base of thesheath 2 acts to redirect the tensioning cable 40 to an off-axis pulley43 and away from the sheath's central lumen 42.

Referring to FIG. 8, the sheath rigidizing linkage structure 60 may runparallel to the core 1 without being coaxial with it. Each link mayinclude dedicated rigidizing features 61 through which a rigidizingcable 62 may run and at least one lateral orifice 62 which, whenmultiply assembled in the complete linkage, form a laterally parallelsegmented lumen through which the core 1 or surgical tools may run. Thelateral orifice 62 has a diameter D3, which is substantially similar todiameter D1, described above.

FIG. 9 depicts a laterally parallel sheath linkage. The laterallyparallel sheath 60 a may form a lateral lumen 70 capable of formingvarying radii of curvature by nesting conical shapes that form thelateral lumen 70, leaving sufficient mechanical clearance 71 toaccommodate an angle .alpha. between adjacent links. The angle .alpha.is preferably in the range from about zero degrees to about 90 degrees.The lateral lumen diameter D4 is substantially similar to diameter D1,described above.

FIG. 10 depicts an alternate embodiment of a linkage. Linkage 82 withthe parallel lateral lumen 70 may include an open side 80 such thatobjects 81 larger than the lumen diameter D4 may be introduced to andwithdrawn from the surgical or diagnostic site using the combinations ofthe open sides 80 to retain therein a matching portion 83 on the object81.

FIG. 11 depicts another alternate embodiment of a linkage. Linkage 82 awith the parallel lateral lumen 70 may employ flexible elements 90 inthe lumen portion of each link that partially overlap each adjacentlink. The flexible elements serve to form a smoother and largersegmented lumen than would be formed by purely rigid links by flexingwhen formed into a radius rather than requiring clearance for the entirerange of motion between the links.

Referring to FIGS. 12A-12G, a mechanism for advancing parallelrigidizing elements may include two opposing racks 91 and 92 thatalternatingly advance relative to each other. Referring to FIG. 12G, themaximum amount of incremental advancement, length ‘L’, is ideallylimited to the length of cannula having the steerable tip 3. A linearlysliding shuttle 93 supports one rack and a housing 94 supports the otherrack. The core actuation handle 95 (not shown for clarity in FIG. 12Aand FIG. 12B) and core rack 91 are each pivotally attached to thehousing 94. The sheath actuation handle 96 and sheath rack 92 are eachpivotally attached to the shuttle 93. The core and sheath actuationhandles 95 and 96 are attached to the rigidizing cables 40 and 34 of thesheath 2 and core 1, respectively. Upon actuation by the user, thesehandles rotate on their pivots 97 and 98 to first relax their respectiverigidizing structure, disengage their respective rack from the other,which remains temporarily fixed, and transmit the force which slides thehousing 94 and shuttle 93 with respect to one another to advance theshape-transferring cannula.

Beginning the advancement sequence as shown in FIG. 12B, spreading thehandholds 99 and 100 (core advancement handhold 100 not shown forclarity) apart biases the core handle 95 (not shown for clarity) againstit's mechanical stop 104 in the housing 94 and rotates the sheath handle96 on its pivot 98, first compressing the sheath rigidizing spring 106,relaxing the sheath linkage 2, and then disengaging the sheath rack 92from the currently-fixed core rack 91. The sheath rack 92 disengages thecore rack 91 by rotating on its pivot 105 against the force of thesheath rack bias spring 113. The sheath rack 92 is rotated away from thecore rack 91 by the force of the sheath rack lifter 115, which extendsfrom the sheath handle 96, acting against the rack's lift tab 117. Aninitial gap between the sheath rack lifter 115 and rack's lift tab 117allows the sheath handle 96 to rotate enough to compress the sheathrigidizing spring 106 and relax the sheath 2 before the sheath rack 92is disengaged from the core rack 91. As illustrated in FIG. 12C,continued spreading of the actuation handles 95 and 96, with racks 91and 92 disengaged, translates the handles apart from each other andadvances the shuttle 93 and sheath 2 relative to the housing 94 and core1.

As illustrated in FIG. 12D, releasing the handle spreading pressureallows the sheath rigidizing spring 106 to rotate the sheath handle 96back to its resting position and re-stiffen the sheath 2 by tensioningthe sheath rigidizing cable 40. The rotation of the sheath handle 96, inturn, rotates the sheath rack lifter 115 away from the sheath rack 92,allowing the sheath rack bias spring 113 to rotate the sheath rack 92towards the core rack 91. Re-engagement of the racks locks the mechanismin a sheath-forward position shown in FIG. 12D.

Continuing the advancement sequence as shown in FIG. 12E, squeezing theadvancement handholds 99 and 100 of the actuation handles 95 and 96 suchthat they rotate towards each other biases the sheath handle 96 solidlyagainst it's mechanical stop 101 on the shuttle 93 and rotates the corehandle 95 on its pivot 97, first compressing the core rigidizing spring102, relaxing the core linkage 1, and then disengaging the core rack 91from the currently-fixed sheath rack 92. The core rack 91 disengages thesheath rack 92 by rotating on its pivot 103 against the force of thecore rack bias spring 112. The core rack 91 is rotated away from thesheath rack 92 by the force of the core rack lifter 114, which extendsfrom the core handle 95, acting against the rack's lift tab 116. Aninitial gap between the lifter 114 and lift tab 116 allows the corehandle 95 to rotate enough to compress the core rigidizing spring 102and relax the core 1 before the core rack 91 is disengaged from thesheath rack 92. The racks 91 and 92 being disengaged from each other,continued squeezing as shown in FIG. 12F translates the handles 95 and96 closer together by advancing the housing 94 and core 1 relative tothe shuttle 95 and sheath 2.

Releasing the squeezing pressure on the advancement handholds 99 and 100allows the core rigidizing spring 102 to rotate the core handle 95 backto its resting position and re-stiffen the core 1 by tensioning the corerigidizing cable 34. The rotation of the core handle, in turn, rotatesthe core rack lifter 114 away from the core rack 91 allowing the corerack bias spring 112 to rotate the core rack 91 towards the sheath rack92. Re-engagement of the racks locks the mechanism in the sheath-backposition shown on FIG. 12A.

Referring to FIG. 12G, the difference in engaged length of the racks 91and 92 between the sheath-back position and the sheath-forward position,length as well as the position of the sliding stop structures 110 and111 in the housing 94 and shuttle 93 define the maximum relative motionfor incremental advancement between the sheath 2 and core 1 elements.The amount of incremental advancement, length is preferably limited tothe length of the steerable tip 3. Rack features 107 such as teethdefine the increments in which the shape-transferring cannula may bemechanically advanced or retracted. The rack features 107 may beconfigured to allow only integral advancement of units the length of theentire steerable tip 3 as shown in FIG. 120 or, alternately, may beconfigured allow units of advancement fractions of that length.

The rack mechanism described above may also withdraw theshape-transferring cannula in controlled increments through a processreversing the advancement sequence. Withdrawal of hand-holds 108 and 109on the ends of the handles 95 and 96 opposite the advancement endsactuate the mechanism in reverse using the same gripping and spreadingfinger/thumb motions used to advance the cannula.

In another embodiment of the invention, FIG. 22 depicts rigidizingstructures including inner and outer concentric tubes, 221 and 222respectively, separated by short segments of materials 223 that changeshape when energized, such as electroactive polymer (EAP), which changesshape when exposed to electric fields. The inner tube 221 may or may nothave an open lumen. When employing biaxially active materials such asEAP, the active material components are oriented to contractlongitudinally and expand radially when energized. The active materialcomponents may be employed in a normally-non-interfering configurationor a normally-interfering configuration. In a normally-non-interferingconfiguration the active material components 223 are each attached toone of the concentric tubes 221 or 222 such that they do not contact theother tube, as shown in FIG. 20a , when not energized. When energized,the radial expansion of the active material components 223 causesmechanical interference with the other tube, as in FIG. 20b , thuspreventing motion between the opposed surfaces 224 and 225 andeffectively locking-in the curvature of the rigidizing structure.According to the present invention, one may substitute materials thatchange shape when exposed to electric current, magnetic fields, light,or other energy sources. The same rigidizing effect may be achieved byreplacing normally-non-interfering active material components 223 withnon-interfering balloons expandable by gas or liquid fluid pressure.Alternately, such materials may be placed in a normally-interferingconfiguration between concentric tubes 221 and 222 such that theyinterfere, as in FIG. 20b when not energized and contract radially tothe state depicted in FIG. 20a when energized. For example, anormally-rigid structure made stiff by normally-interfering EAPcomponents 223 may be made flexible by applying a voltage to the EAPcomponents such that they contract radially to the non-interfering statedepicted in FIG. 20a , relieving the mechanical interference andallowing relative motion between the opposed surfaces 224 and 225 of theconcentric tubes 221 and 222. Similarly, normally-interfering balloonsreplacing normally-interfering active material components 223 may becollapsed by applying a relative vacuum.

Referring to FIG. 13A, in an alternate embodiment of the invention, therigidizing sheath 2 can include rotating wedge links 130. The wedgelinks 130 have hollow central axes 131 that form the sheath's lumen 42as well as two interface features 132 angled with respect to oneanother. For example, the angle between the links can be between aboutzero degrees and about 90 degrees. The perpendicular centerlines 133 ofthe interface surfaces define axes of rotation between the links. Asdepicted diagrammatically in FIGS. 13B and 13C, the wedge links 130 in asample starting position in FIG. 13B rotate with respect to neighboringlinks 134 at the connecting interface 132 between links. This rotationforms curves as shown in FIG. 13C in the sheath 2 structure whilemaintaining a substantially constant sheath lumen 42 volume. Impedingrotation between links rigidizes the structure. Link rotation can beprevented through any of the ways described above for impeding relativemotion between links. The wedge links 130 may be formed as sections ofspheres as shown in FIG. 13A to avoid creating sharp corners when curvesare formed, leaving a relatively smooth and atraumatic outer surface.

FIGS. 14A-14C depict another embodiment of the invention in which one ofthe two parallel elements in the shape-transferring cannula is passive.The passive element is more rigid than the relaxed rigidizing structureand more flexible than the stiffened rigidizing structure. The passiveelement is less mechanically complex than an equivalent rigidizingstructure, not requiring rigidizing cables 34 and 40 or other mechanismsto serve the shape-transfer function. Thus a shaped cannula assemblywith a passive sheath may be narrower in cross-section than an assemblyformed of two rigidizing structures. In FIG. 14A the core 1 is relaxedsuch that it is more flexible than the sheath 2 and has been advancedsuch that the steerable tip 3 protrudes ahead of the sheath 2. In FIG.14B the core 1 is stiffened such that it is more rigid than the sheath 2and the user deflects the steerable tip 3 towards the direction ofintended cannula advancement. In FIG. 14C the core 1 remains stiffenedsuch that it is more rigid than the sheath 2 and the sheath is thenadvanced over the core and its steerable tip 3. The sheath 2 assumes thecore's longitudinal shape including the new bend introduced by the userthrough the deflected steerable tip 3. Elements of a passive linkstructure could be mechanically energized to encourage them to moverelative to one another when being advanced past a relatively rigidstructure. Mechanical energizing can be achieved by vibrating thepassive structure with any suitable device, such as a piezoelectrictransducer, voicecoil, or eccentrically weighted motor.

Embodiments of the invention that employ continuous, non-segmented,parallel core and sheath structures can be made smaller in cross-sectionthan mechanically-stiffened linkage structures. Such structures may beconstructed such that they become relatively rigid when energized orbecome relatively flexible when energized.

FIG. 15 depicts a continuous, parallel shape-transferring core andsheath structure. The core 1 and sheath 2 structures can each includeinner 151 and outer 152 flexible tubes containing stiffening material153 that increases in viscosity or otherwise stiffens when energized.Examples of such substances are electrorheological fluid, which stiffensupon exposure to electrical potential, and magnetorheological fluid,which stiffens upon exposure to magnetic fields. A rigidizing structureconfigured as a core or as a sheath may be built-up of inner 151 andouter 152 containment tubes with stiffening material 153 sandwiched inbetween. In the case of a core, the inner tube may be a solid elementsuch as plastic monofilament, lacking a lumen. In the case of astructure employing electrorheological fluid, flexible electricalcontacts may line the length of each containment tube or the tube itselfmay be made of electrically-conductive plastic or other similarmaterial. A section of electrically insulating material 154 may connectthe tubes 151 and 152 at their proximal and distal ends, mechanicallyconnecting the tubes 151 and 152 and sealing the electrorheologicalfluid within. A woven mesh or other similar separating material 155sandwiched with the electrorheological fluid between the tubes 151 and152 may act as a baffle, restricting the flow of viscous fluid so as toincrease the rigidity of the structure when energized, and as aninsulator when an electrical potential is used to energize the elements.The tubes 151 and 152 themselves may contain baffling features such asgrooves or threads and may also contain a layer of insulating material,obviating the need for a separating material 155. A similar structureemploying magnetorheological fluid could be constructed with at leastone containment tube containing electrical conductors arranged in such amanner as to generate a magnetic field sufficient to rigidize thestructure.

A shape-transferring cannula structure may be constructed ofnormally-rigid core 1 and sheath 2 elements which, in proper sequence,become flexible when energized and re-stiffen when they return to anun-energized state. Each element can become flexible enough, whenenergized, to be advanced along a relatively rigid mating structure andthen, when de-energized, become rigid enough to mechanically support theadvancement of an energized parallel structure. Referring to FIG. 16,parallel normally-rigid core 1 and sheath 2 elements may include intheir construction thermoplastic, thermoplastic alloys such as Kydex™(acrylic-PVC alloy), urethane alloys, or similar materials that softento a flexible state when heated above a transition temperature byembedded heating elements 171 and 172 or any suitable mechanism. Thetransition temperature can be selected through design and materialcomposition to be somewhat higher than normal body temperatures. Thenormally-rigid parallel structures may contain heating elements thatmomentarily increase their temperatures above the flexibility transitiontemperature. Surrounding body fluid such as blood, saline solution, orlymph can serve as a heat sink to quickly draw heat away and re-stiffenthe structures when the momentary heating is ceased. Similarly, as shownin FIG. 23, normally-rigid core 1 or sheath 2 structure can include aguidewire 260 with wirewound coils in its construction. The coils 263can be at least partially potted in a low-temperature flowing material261 such as wax or polymer which adheres to the coils. Thelow-temperature flowing material 261 may be contained within a compliantcover 262. In an un-energized state the flowing material 261 isrelatively solid and prevents the coils 263 from moving substantiallywith respect to one another, thus substantially locking-in the curvatureof the structure. When energized through heating, the flowing material261 softens sufficiently to allow relative motion between coils 263,thus relaxing the structure.

Referring to FIGS. 19A and 19B, shape-transferring cannula can be builtof normally-rigid core 1 and sheath 2 structures, each includingflexible tubes 212 and 214 respectively, containing substantially stiffmaterials 213 that relax upon vibration. Such materials can includeinterlocking particles like sand grains or normally-viscous fluid, suchas xanthan gum that becomes less viscous upon agitation. Vibrating eachstructure, for example with a vibrating element 215 such as apiezoelectric transducer, a voicecoil, or a motor with an eccentricallymounted weight, could temporarily relax it to a flexible state byloosening the interlocking particles or by causing the contained fluidto transition to a less viscous state. Alternatively, the containmenttubes 212 and 214 themselves could be constructed of or contain apiezoelectric material such as PVDF (polyvinylidene fluoride) alongtheir length such that each entire tube could actively vibrate whenenergized with an alternating voltage V.

In another embodiment of the invention, FIG. 22 depicts rigidizingstructures including inner and outer concentric tubes, 221 and 222respectively, separated by short segments of materials 223 that changeshape when energized such as electroactive polymer (EAP), which changesshape when exposed to electric fields. The inner tube 221 may or may nothave an open lumen. When employing biaxially active materials such asEAP, the active material components are oriented to contractlongitudinally and expand radially when energized. The active materialcomponents may be employed in a normally-non-interfering configurationor a normally-interfering configuration. In a normally-non-interferingconfiguration, the active material components 223 are each attached toone of the concentric tubes 221 or 222 such that they do not contact theother tube, as shown in FIG. 20A, when not energized. When energized,the radial expansion of the active material components 223 causesmechanical interference with the other tube, as illustrated in FIG. 20B,thus inhibiting or preventing motion between the opposed surfaces 224and 225 and effectively locking-in the curvature of the rigidizingstructure. The same invention may substitute materials that change shapewhen exposed to electric current, magnetic fields, light, or otherenergy sources. The same rigidizing effect may be achieved by replacingnormally-non-interfering active material components 223 withnon-interfering balloons expandable by gas or liquid fluid pressure.Alternately, such materials may be placed in a normally-interferingconfiguration between concentric tubes 221 and 222 such that theyinterfere, as in FIG. 20B when not energized and contract radially tothe state depicted in FIG. 20A, when energized. For example, anormally-rigid structure made stiff by normally-interfering EAPcomponents 223 may be made flexible by applying a voltage to the EAPcomponents such that they contract radially to the non-interfering statedepicted in FIG. 20A, relieving the mechanical interference and allowingrelative motion between the opposed surfaces 224 and 225 of theconcentric tubes 221 and 222. Similarly, normally-interfering balloonsreplacing normally-interfering active material components 223 may becollapsed by applying a relative vacuum.

Referring to FIG. 17A, core and sheath rigidizing 180 structures caninclude compliant inner and outer tubes, 181 and 182, containingcompression-stiffening particles 183 in the annular space between theopposing tube surfaces. The compression stiffening particles 183 aremade of materials such as expanded polystyrene that interlock and form asubstantially rigid structure when compressed. Such compression canoccur when the space containing the compression-stiffening particles isplaced under a relative vacuum P. Alternatively, external pressure maybe applied to the material in the annular inter-tubal space to compressand stiffen it. For example, pressure may be applied to the internalconcentric tube such that it expands and presses compression-stiffeningmaterial in the inter-tube space against the external concentric tube.Referring to FIG. 17B, core 1 structure can include a compliant tube 184containing compression-stiffening particles 183. The structure may bestiffened by putting the tubes interior under relative vacuum P.

Referring to FIG. 18, a core 1 or sheath 2 structure including links 191may be rigidized or relaxed via pressure P which can be either positivepressure or relative vacuum. In a normally-rigid configuration, acompliant cover 192 the length of the structure can be stretched tautagainst the movable links 191 in an equalized pressure environment. Thetight covering 192 keeps the links from moving substantially relative toone another, making the rigidizing structure stiff. Application ofpressure P underneath the compliant cover 192 expands the cover,allowing the links 191 to rotate relative to one another therebyrelaxing the structure. Alternately, in a normally-flexible structure,the compliant cover 192 can loosely cover the links 191 in an equalizedpressure environment such that the links can rotate relative to oneanother. Applying a relative vacuum P inside the compliant cover 192causes it to compress against the movable links 191, preventing theirrotation relative to one another thereby stiffening the structure.

The rigidizing structures described above as a paired system may be alsoemployed singly as an alternatingly rigid and compliant support for asteerable catheter such as an endovascular catheter or flexibleendoscope. In such cases as depicted in FIG. 21, the rigidized structureprovides support for the catheter to round corners without thepossibility of looping because the flexible element is advanced onlywhen the supporting structure is rigid. Similarly, the relaxedrigidizing support is advanced only along the length of the catheter,using it as a guidewire.

In another embodiment of the invention, a steerable catheter such as anendovascular catheter or flexible endoscope may be aided in advancingaround tight corners through alternating between advancement of twoparallel structures, using the relatively rigid steerable bendingsection at the tip to advance through a tight anatomical turn withoutlooping.

In one embodiment, the sheath is rigidized and the core with anarticulating tip is made flexible. The core is advanced and thenrigidized. The articulating tip is pointed in the desired direction ofpath creation. The sheath is relaxed and advanced over the rigid core.

Referring now to FIG. 24, yet further aspects of the present inventionare illustrated. More specifically, FIG. 24 illustrates that thehandholds, such as handholds 99, 100, 108, 109 illustrated in FIGS.12A-12H, can optionally be replaced with a semi- or fully automatedsystems, to permit the practitioner's hands to be used for other tasksduring the particular procedure performed on a patient. As illustratedin FIG. 24, a rack 302 having teeth 304 is pivotally mounted to the arm306 at a pivot 308, to which handhold 100 is attached in the embodimentillustrated in FIG. 12G. A pinion 310 having teeth 316, which mate withteeth 304, is rotatably mounted to arm 312, while a pin or the like 314holds the rack 302 against the pinion. Thus, rotation of pinion 310,such as by a rotary motor 318 or the like, causes arm 306 to move indirection X, while the arm 312 can be separately or simultaneously movedalong direction X by pulling or pushing on the arm 312, or the motor318, with a suitable linear actuator or motor (not illustrated). Furtheroptionally, the activation of the actuators or motors, including motor318, can be automated by controlling them using an automatic controller320. By way of example and not of limitation, controller 320 can be ageneral purpose computer having a memory 322 in which the logic of thesequence of movements of the arms 306, 312 can reside. Alternatively,controller 320 can be a PLC controller or other controller as will bereadily appreciated by those of skill in the art, which canautomatically control the movements of the arms 306, 312.

FIG. 25 shows a cross-sectional view of an embodiment of a cannulasystem 2500 with a rigidizable structure and distal tensioning-cablerecirculation. A static tension anchor 2505 is coupled to a tensioningelement 2510. The tensioning element 2510 may be a wire, filament, ormulti-stranded cable. The tensioning element may also have a sheath orcoating to improve its lubricity (e.g., fluorocarbon polymer). Thetensioning element passes through a dynamic tensioning anchor 2515,nested links 2520, terminal link 2525, and a recirculating guide 2530;thus linking them together. The tensioning element 2510 is attached tothe static tensioning anchor 2505 at two points, but it is able to slidefreely through the dynamic tensioning anchor 2515, nested links 2520,terminal link 2525, and a recirculating guide 2530.

In a preferred mode of operation, the cannula system 2500 is rigidizedby holding the static tension anchor 2505 in a fixed position while thedynamic tension anchor 2515 is moved to compress the array of nestedlinks 2520. Since the tensioning element 2510 forms a loop through therecirculating guide 2530, the displacement of the recirculating guide2530 and the terminal link 2525 is not a function of the compression ofthe nested links 2520, the rigidization of the cannula system 2500 andthe accommodation of the shortening of the cannula system 2500 due tocompression is accomplished through the displacement of the dynamictension anchor 2515.

The distal recirculating guide 2530 will have a displacement that isgoverned primarily by the pretension slack and stretching of thetensioning element 2510. For a cannula system having nested links 2520that are fabricated from material (e.g., organic polymer) with a lowelastic modulus, the distal displacement is considerably smaller inmagnitude than the change in length of the cannula system whenrigidized. Also, the distal recirculating architecture increases theeffective flexibility of the distal linkage by minimizing the length ofcable that must be slid through the cable channels when the distallinkage is put into a turn (e.g., by being slid over an endoscopesteering tip).

FIG. 26 shows a cross-sectional view of an embodiment of a cannulasystem 2600 with a rigidizable structure and proximal recirculation. Astatic tension anchor 2605 is coupled to a proximal recirculation guide2630 that houses a tensioning element 2610. The tensioning element 2610may be a wire, filament, or multi-stranded cable. The tensioning elementmay also have a sheath or coating to improve its lubricity. Thetensioning element passes through a dynamic tensioning anchor 2615,nested links 2620, and is attached to terminal link 2625; thus linkingthem together. The tensioning element 2610 is attached to the terminallink 2625 at two points, but it is able to slide freely through thedynamic tensioning anchor 2615, nested links 2620, and proximalrecirculating guide 2630.

In a preferred mode of operation, the cannula system 2600 is rigidizedin a manner similar to that described for the cannula system 2500. Thestatic tension anchor 2605 is held in a fixed position while the dynamictension anchor 2615 is moved to compress the array of nested links 2620.Displacement of the distal end (terminal link 2625) is governedprimarily by the elasticity and slack of the tensioning element 2610,whereas the shortening of the cannula system due to interlink gapclosure and link deformation is accommodated by the displacement of thedynamic tension anchor 2615. This configuration creates a more flexibleproximal section as the least length of tensioning wire is required tocirculate for a proximal bend (whereas the entire wire would have torecirculate for a distal bend).

FIG. 27 shows a cross-sectional view of an embodiment of a cannulasystem 2700 with a rigidizable structure and dual recirculation. Astatic tension anchor 2705 is coupled to a proximal recirculation guide2735 that houses a tensioning element 2710. The tensioning element 2710may be a wire, filament, or multi-stranded cable. The tensioning elementmay also have a sheath or coating to improve its lubricity. Thetensioning element passes through a dynamic tensioning anchor 2715,nested links 2720, terminal link 2725, and a recirculating guide 2730;thus linking them together. The tensioning element 2710 is not attachedto any of the components of the cannula system 2700 and is able to slidefreely through the dynamic tensioning anchor 2715, nested links 2720,proximal recirculating guide 2735, and distal recirculating guide 2730.This configuration creates the most flexible linkage as it shortens therecirculation distance for the tensioning cables to no more than ½ thelength of the linkage.

In a preferred mode of operation, the cannula system 2700 is rigidizedin a manner similar to that described for the cannula systems 2500 and2600. The static tension anchor 2705 is held in a fixed position whilethe dynamic tension anchor 27615 is moved to compress the array ofnested links 2720. Displacement of the distal end (distal recirculatingguide 2730) is governed primarily by the elasticity and slack of thetensioning element 2710, whereas the shortening of the cannula systemdue to interlink gap closure and link deformation is accommodated by thedisplacement of the dynamic tension anchor 2715.

FIG. 28 shows the distal end 2800 of an embodiment of a rigidizablecannula system similar to the cannula system 2500 of FIG. 25. In thisembodiment, a tensioning element 2815 and a tensioning element 2816traverse nested links 2805, wiper link 2810 and distal recirculatingguides 2820 and 2821. Wiper link 2810 has a distal aperture 2825 that isnarrower than that of the nested links 2805. The narrow aperture 2825 ofthe wiper link 2810 provides a close tolerance clearance for an insertedinstrument that helps prevent the induction of material into the gapbetween the wiper link 2810 and an inserted instrument. The narrowaperture also provides better direction control over the tip of aninserted instrument as it is advanced.

FIG. 29 shows an inner rigidizable linkage 2940 providing a conduit foran endoscope 2905 with a steerable tip 2910 coupled an endoscope tipliner 2915 by a gasket 2920. The endoscope tip liner 2915 provides asurface that allows the endoscope tip 2915 to slide freely within anouter rigidizable linkage 2935. In one embodiment the endoscope tipliner 2915 is constructed from helical mesh. The endoscope tip liner maybe sized so that it fits within and fills a gap between a wiper link2930 and the endoscope 2905. The gasket 2920 may also couple an externalcover 2925 to the steerable tip 2910.

FIG. 30A shows an embodiment of a cannula system 3000 having anendoscope 3001 coupled to handles 3002 and 3010 that serve as supportfor two independent actuating systems. Handle 3010 supports static plate3011 that is similar to static tension anchor 2505 of FIG. 25. Dynamicplate 3012 is similar to dynamic tension anchor 2515 of FIG. 25, and iscoupled to static plate 3011 by actuators 3013 and 3014 (e.g., aircylinders). Dynamic plate 3012 is coupled to, and serves to compress anouter linkage 3020 that runs concentrically over rigidizable linkage3015. Actuators 3013 and 3014 serve to axially separate static plate3011 and dynamic plate 3012, thus providing the operation as describedwith respect to FIG. 25. Handle 3002 supports static plate 3004, whichis in turn coupled to dynamic plate 3003 by actuators 3005 and 3006(e.g., air cylinders). Actuators 3005 and 3006 serve to axially separatestatic plate 3004 and dynamic plate 3003, thus providing the operationas described with respect to FIG. 25. A cannula 3008 that includes arigidizable linkage 3015 similar to 2520 of FIG. 25 is attached todynamic plate 3003.

FIG. 30B shows the cannula system 3000 of FIG. 30A in a retractedconfiguration. Handle 3003 has been displaced with respect to handle3010 so that a greater portion of the rigidizable linkage 3015 resideswithin outer linkage 3020.

FIG. 31A shows an embodiment of a cannula system 3100. A reference framehandle 3105 supports a static anchor plate 3125 that is coupled toactuators 3110 and 3115 (e.g., air cylinders). A rigidizable linkage3130 is coupled to dynamic anchor plate 3120. Cannula system 3100 issimilar to system 2500 of FIG. 25. Actuators 3110 and 3115 are inactiveand the rigidizable linkage 3130 is in a relaxed state.

FIG. 31B shows the cannula system 3100 of FIG. 31A in a rigidizedconfiguration. Actuators 3110 and 3115 are active, and the separationbetween static anchor plate 3125 and dynamic anchor plate 3120 isincreased, thereby rigidizing the rigidizable linkage 3130.

The reference frame handle 3105 allows a user to establish the relativeposition of the endoscope 3101 and the rigidizable linkage 3130 toexpose a length L1 of the tip of the endoscope 3101. L2 is the distancefrom the tip of the rigidizable linkage 3130 to the handle. L2 isessentially constant, whether the rigidizable linkage 3130 is in arelaxed or rigidized state. At. The rigidizable linkage 3130 may berigidized without substantially altering L2, while essentiallymaintaining the exposed tip length L1 without having to adjust theposition of endoscope 3101 during the rigidization process.

FIG. 32 depicts a flow diagram of a method for rigidizing a cannulasystem in conjunction with an endoscope. In step 3205 an endoscope isaxially displaced with respect to a surrounding rigidizable cannula toexpose a specific length of a tip of the endoscope. At the same time arelative position between a handle of the cannula system and theendoscope is established. In step 3210 actuators are activated torigidize a cannula while maintaining the previously established exposedlength of the endoscope tip and relative position between the handle ofthe cannula system and the endoscope.

FIG. 33A shows an embodiment of a cannula system 3300 similar to thatshown in FIG. 31A. A handle 3305 is coupled to a rigidizable linkage3310 that acts as a conduit for an endoscope 3301. An inflatable balloon3315 is coupled to the distal tip of rigidizable linkage 3310. Whilelinkage 3310 is rigidized to support advancement of the endoscope 3301,the balloon 3315 may be inflated such that it engages a lumen,especially in mobile tissue such as the small bowel, so as to locallyimmobilize it such that endoscope 3301 may advance through the lumenefficiently. Balloon 3315 may then be deflated to advance linkage 3310along endoscope 3301. Alternately, balloon 3315 may be used to hold theposition of linkage 3310 relative to mobile tissue when linkage 3310 isrelaxed for repositioning (e.g. for scope “straightening”).

FIG. 33B shows an embodiment of a cannula system 3302 that is similar tothe cannula system 3300 shown in FIG. 33A, but whose rigidizable linkage3330 serves as a conduit for endoscope 3320 that includes an inflatableballoon 3345. A balloon 3335 is coupled to the distal tip of therigidizable linkage 3330 and a balloon 3345 is coupled to the endoscope3320 proximal to the steering tip 3340. Balloon 3345 may be inflated toengage a lumen and hold position of mobile tissue such as the smallbowel while the rigidizable linkage 3330 is made flexible and advancedover the endoscope 3320.

While the invention has been described in detail with reference topreferred embodiments thereof, it will be apparent to one skilled in theart that various changes can be made, and equivalents employed, withoutdeparting from the scope of the invention. Each of the aforementioneddocuments is incorporated by reference herein in its entirety.

What is claimed is:
 1. A medical cannula system comprising: a conduit;an endoscope comprising a distal steerable tip, wherein the endoscope isinside the conduit, and wherein the distal steerable tip of theendoscope extends out of the conduit; a tip liner surrounding the distalsteerable tip of the endoscope; and a wiper link surrounding the tipliner at a close tolerance.
 2. The medical cannula system of claim 1,further comprising: an outer linkage comprising a distal end; whereinthe wiper link is at the distal end of the outer linkage.
 3. The medicalcannula system of claim 1, further comprising: an outer linkage thatsurrounds the conduit.
 4. The medical cannula system of claim 1, furthercomprising: an outer linkage that surrounds the conduit; wherein theouter linkage is rigidizable.
 5. The medical cannula system of claim 1,further comprising: a gasket between the distal steerable tip of theendoscope and the tip liner.
 6. The medical cannula system of claim 1,further comprising: an outer cover that surrounds the conduit; and agasket coupled between the outer cover and the distal steerable tip ofthe endoscope.
 7. The medical cannula system of claim 1: wherein theconduit is rigidizable.
 8. The medical cannula system of claim 1:wherein the tip liner comprises a mesh.
 9. The medical cannula system ofclaim 1: wherein the tip liner comprises a helical mesh.
 10. A medicalcannula system comprising: an outer linkage comprising a distal end; anendoscope comprising a distal steerable tip that extends out of thedistal end of the outer linkage; and a wiper link at the distal end ofthe outer linkage and that surrounds the distal steerable tip of theendoscope at a close tolerance.
 11. The medical cannula system of claim10, further comprising: a tip liner that surrounds the distal steerabletip of the endoscope.
 12. The medical cannula system of claim 10,further comprising: a tip liner that surrounds the distal steerable tipof the endoscope; wherein the tip liner comprises a mesh.
 13. Themedical cannula system of claim 10, further comprising: a tip liner thatsurrounds the distal steerable tip of the endoscope; wherein the tipliner comprises a helical mesh.
 14. The medical cannula system of claim10, further comprising: a tip liner that surrounds the distal steerabletip of the endoscope; and a gasket between the steerable tip and the tipliner.
 15. The medical cannula system of claim 10, further comprising: atip liner that surrounds the distal steerable tip of the endoscope;wherein the tip liner is between the distal steerable tip of theendoscope and the wiper link; and wherein the wiper link surrounds thetip liner at a close tolerance.
 16. The medical cannula system of claim10: wherein the outer linkage is rigidizable.
 17. The medical cannulasystem of claim 10, further comprising: a conduit that surrounds theendoscope; wherein the distal steerable tip of the endoscope extends outof the conduit.
 18. The medical cannula system of claim 10, furthercomprising: a conduit that surrounds the endoscope; wherein the conduitis rigidizable.
 19. The medical cannula system of claim 10, furthercomprising: an outer cover that surrounds the outer linkage; and agasket coupled between the outer cover and the distal steerable tip ofthe endoscope.
 20. A medical cannula system comprising: an outer linkagecomprising a distal end; a conduit inside the outer linkage; anendoscope comprising a distal steerable tip, wherein the endoscope isinside the conduit, and wherein the distal steerable tip of theendoscope extends out of the conduit; a tip liner surrounding thesteerable tip; a gasket between the distal steerable tip of theendoscope and the tip liner; and a wiper link at the distal end of theouter linkage and surrounding the tip liner at a close tolerance.